The traditional plug comparators have a protection and support structure including a casing or nose which has openings for the passage of the feeler elements. The feeler elements are fastened in an adjustable manner to the arms in order to permit the use of the comparator in different measurement ranges. This adjustability may also require the use of different casings.
To the base of the nose there is usually fastened by screws a closure plate which has the two-fold purpose of mechanically protecting the inner elements of the comparator and of reducing the possibility of foreign matter, for instance, chips, powder and cooling liquids used in the machining of the parts, from accidentally entering the comparator.